The heart is a muscular pump made
up of four chambers. The two upper chambers are called
atria. The two lower chambers are called ventricles. A natural electrical
system causes the heart muscle to contract. This pumps blood through the heart to
the lungs and the rest of the body.

Why It Is Done

An
EKG is done to:

Check the heart's electrical activity.

Find the cause of unexplained chest pain or pressure. This could be caused
by a heart attack, inflammation of the sac surrounding the heart (pericarditis), or
angina.

Find the cause of symptoms of
heart disease. Symptoms include shortness of breath, dizziness, fainting, and heartbeats that are rapid and
irregular (palpitations).

Find out if the walls of the
heart chambers are too thick.

Check how well
medicines are working and see if they are causing side effects that affect the
heart.

Check how well mechanical devices that are implanted in the
heart, such as
pacemakers, are working. These devices help to control the
heartbeat.

Check the health of the heart when other diseases or
conditions are present. These include
high blood pressure,
high cholesterol, cigarette smoking,
diabetes, and a family history of early heart
disease.

How To Prepare

Be sure to tell your doctor about all the medicines you take, even over-the-counter ones. Many medicines can change the results of this test.

Remove all jewelry from your neck, arms, and wrists. Men are usually
bare-chested during the test. Women may often wear a bra, T-shirt, or gown. You will be given a cloth
or paper covering to use during the test.

Talk to your doctor
about any concerns you have regarding the need for the test, its risks, how it
will be done, or what the results will mean. To help you understand the
importance of this test, fill out the
medical test information form(What is a PDF document?).

How It Is Done

You may get an EKG at your health professional's office or during a
series of tests at a hospital or clinic. EKG equipment is often portable. This means
the test can be done almost anywhere. If you are in the hospital, your heart
may be constantly monitored by an EKG system.

During an EKG:

You will lie on a bed or table. Certain areas of your
arms, legs, and chest will be
cleaned and may be shaved. This provides a clean, smooth surface to attach the
electrodes.

Several electrodes are
attached to the skin on each arm and leg and on your chest. These are hooked to a
machine that traces your heart activity onto a paper. If an older machine is
used, the electrodes may be moved at different times during the test. This measures
your heart's electrical activity from different places on your chest.

You will be asked
to lie very still and breathe normally during the test. Sometimes you may be
asked to hold your breath. You should not talk during the test.

After
the test, the electrode paste is wiped off.

The test
usually takes 5 to 10 minutes.

How It Feels

The electrodes may feel cool when they
are put on your chest. If you have a lot of hair on your chest, a small area
may need to be shaved to put the electrodes on. When the electrodes are taken
off, they may pull your skin a little.

Risks

An EKG is a completely safe test. In most
cases, there is no reason why you should not be able to get an EKG.

The electrodes are used to transfer an image of your heart's electrical activity
to the tracing on paper. No electricity passes through your body from
the machine, and there is no danger of electrical shock.

Results

An electrocardiogram (EKG or ECG) is a
test that checks for problems with the electrical activity of your heart. An
EKG shows the heart's electrical activity as line tracings on paper. The spikes and dips in the line tracings are called waves.

The heart beats in a regular rhythm, usually
between 60 and 100 beats per minute.

The tracing looks normal.

Abnormal:

The heart beats too slow (such as less than 60 beats
per minute).

The heart beats too fast (such as more than 100 beats per
minute).

The heart rhythm is not regular.

The tracing does not look
normal.

What Affects the Test

You may not be able to
have the test, or the results may not be helpful, if:

The electrodes are not securely attached to
your skin.

You move or talk during the
test.

You exercise before the test.

You are anxious or
breathe very deeply or rapidly during the test.

What To Think About

Sometimes your EKG may look normal even when
you have heart disease. For this reason, the EKG should always be looked at
along with your symptoms, past health, and a physical exam. If needed,
other test results should be looked at too.

A stress EKG
is a type of EKG done during exercise. A resting EKG is always done before an
exercise EKG test. Results of the resting EKG are compared to the results
of the exercise EKG. A resting EKG may also show a heart problem that would
make an exercise EKG unsafe. To learn more, see the topic
Exercise Electrocardiogram.

EKGs are not recommended for people who are healthy and have no symptoms of heart disease.footnote 1

If your doctor recommends a test, ask what it is for and why you need it. You can help decide if a test is right for you. Talk with your doctor to make that decision. To learn more, see Heart Tests: When Do You Need Them?

This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.